1. Field of the Invention
The present invention relates to methods and apparatus for the construction of supports for staircase treads. More particularly, the present invention provides a form for the construction of curved stringers and banisters for staircases.
2. Discussion of Related Art
Axially-mounted helical jigs for forming the stringers that support treads on a curved staircase are well-known, as shown in U.S. Pat. No. 3,879,026. In this disclosure, the stringers are formed on radial clamp arms that are pivotably mounted on a central pipe. The pipe is suspended horizontally between two bearings that hold the arms above the floor.
The rotational position of the arms about the pipe is then carefully adjusted so that the arms form a sequence of equal angles about the pipe. The proper rotational adjustment of the arms is determined using a plumb bob and protractor. The position of the arms along the pipe and the stringer clamps along the length of the radial clamp arms must also be individually adjusted to accommodate the desired radius.
These multiple adjustments of the helical jig are time consuming, but critically important to the appearance of the completed staircase. Furthermore, this jig forms only one of the curved staircase elements at a time.
In contrast, the helical jig disclosed in U.S. Pat. No. 3,902,948 does not require assembly by highly skilled workmen, because it connects horizontal braces between posts on the radial arts of the jig to assure correct positioning of the parts of the jig. However the addition of these posts and braces, and their attendant brackets and fasteners, greatly increases the amount of time required to assemble this jig. Furthermore, this jig also only forms one of the curved staircase elements at a time.